BS ISO 6344-3:2021 pdf free download – Coated abrasives – Determination and designation of grain size distribution Part 3: Microgrit sizes P240 to P5000.
After adjustment, fill the water jacket and connect it to a thermostat.
5.3.1.2 Test temperature
The testing of the grain size distribution shall be carried out under constant temperature with a permissible deviation of ±0,1 °C.
It is convenient to use a test temperature of 25 °C. The grain diameters indicated in Tables A.1 and A2 for the respective times of sedimentation apply to this temperature only.
For the determination of the grain diameters for other test temperatures, see S.L51.
5.3.1.3 Adjustment of the sedimentation medium
The methyl alcohol used for the test shall be adjusted by means of the checking mineral 320.
The grain sizes corresponding to 10 %, 20 %, 30 %, 40 % and 50 % points shall not deviate by more than ±0,5 im from the values specified on the curves supplied with the checking mineral. The average of the algebraic sum of the deviations shall not exceed ±0,3 urn.
If an agreement with the accompanying curves is not reached within the permissible tolerances, then the density and viscosity of the sedimentation medium shall be changed such that an agreement is obtained.
5.3.2 Preparation of the test portion
Sampling and splitting of abrasive grains shall be in accordance with ISO 9138.
Prior to the test, the test portion shall be heated to a temperature of 600 °C ± 20 °C for at least 10 mm.
5.4 Procedure
5.4.1 Filling of sedimentation tube
Fill the sedimentation tube with the previously adjusted sedimentation liquid to a height of 1 000 mm ±2 mm (measured from the bottom of the collecting tube). Allow it to stand until equilibrium is reached between the water jacket connected to the thermostat and the sedimentation tube temperatures.
5.4.3 Transfer to sedimentation tube
Place a suitable funnel in the sedimentation tube. Shake the test tube containing the test portion and the sedimentation liquid vigorously for at least 30 s. Then, pour its contents onto the sedimentation liquid, down the slope of the funnel.
Subsequently, quickly remove the funnel from the sedimentation tube in order to prevent any residue from dropping into the tube as this would distort the results.
5.4.4 Start of measurement
Measurement shall begin at the time of transfer of the test portion.
For the theoretical equivalent grain diameters, d, for grits of fused aluminium oxide and for grits of silicon carbide see Annex A.
5.4.5 Determination of the maximum grain size
For the determination of the maximum grain size, the time period is measured between the transfer of test portion to the tube (start of measurement) and the moment when the first grain reaches the bottom of the collecting tube.
The grain size of fused aluminium oxide can be determined according to Table A.1 and the grain size for silicon carbide according to Table A.2.
The diameter of the first sedimented grain is the do value (first grain).
If the permissible do value is exceeded, the test shall be repeated with one or more new test portions.
Check for agglomeration.
5.4.6 RecordIng measurement values
The initial point of the grain size distribution curve is the time when the first continuous flow of particles reaches the bottom of the collecting tube. Check for agglomeration.
The time shall be recorded when the volume between the measurement lines is filled. This shall be detected when the surfaces of the grains are reaching the measurement line.
To avoid the error in reading, the view on the tube needs to be in line with the measurement lines. The end point of measurement is that time when all the particles have settled, i.e. when the height of sedimentation is no longer changing.